Marieke ten Broeke has worked as a proficiency test assistant at KWR since 1999. Among other things, she is responsible for daily operations. This involves running the administration, drafting correspondence, preparing the result files and instructions for test participants, and preparing the reports. Marieke also mans the proficiency test help desk. She is the first point of contact for participants, answering their questions, particularly regarding practical organisational matters; she redirects substantive questions to the relevant experts. Marieke also assists the proficiency test coordinator with PR tasks and the elaboration of the annual programme and the newsletter.